In conventional floppy disc, an index signal indicates start and finish of a track, and this indication is carried out by optically detecting an index hole provided in a case.
A floppy disc of 3.5" has been recently developed and this is not provided with an index hole. Therefore an index signal issue mechanism should be independent. In a case of a direct drive, a rotor of a flat motor is utilized, and in a case of a belt drive, a pulley secured to the spindle is utilized, and the index signal issue mechanism is formed optically or magnetically.
In the above mentioned index signal issue mechanism, when the rotor or pulley is secured on the spindle it is necessary to perform their alignment with a driving pin projecting on a spindle hub, and engaging a drive hole of a metal hub in the center of the magnetic disc. This operation is very troublesome.
In view of these circumstances, the present invention is to provide an index signal issue mechanism of a magnetic record and reproduction device which does not require any adjustment when the mechanism is set up.